The last decade has witnessed a change in the production of livestock and dairy products from small, family owned units, to large corporate owned farms. As a direct result of this evolution, large wastewater ponds have been constructed to consolidate waste handling and remediation. However, the increased production of these large farms has also resulted in increased waste which directly impacts air and water quality in the surrounding area.
Because of economic constraints, livestock production units typically utilize large anaerobic earthen or concrete storage basins. These large basins ponds can be sources of air and water pollution. Anaerobic decomposition produces carbon dioxide, methane, (one of the greenhouse gases); hydrogen sulfide, (of concern because of its toxicity and odor); and ammonia. The smell of nearby manure decomposition is particularly offensive, and has created concerns throughout the livestock and dairy industry.
The impact of an organic waste discharged into a stream, lake, or underground aquifer can be predicted by the measurement of dissolved oxygen (DO), ammonia nitrogen (NH3-N), and biological chemical oxygen demand (BOD) in the waste water source. Livestock waste streams typically have BOD concentrations in excess of 5000 mg/L compared with approximately 200 mg/L for municipal wastewater. The high BOD levels of livestock waste prohibit any discharge into receiving streams by livestock and dairy production units. Municipalities are regulated by state and federal permit standards as to the BOD TSS and NH3-N limits allowed to be discharged into receiving streams. Liquid manure tends to have the majority of its nitrogen in the ammonia form (NH3-N).
In anaerobic storage and decomposition, organic nitrogen is continually being converted to ammonia and a portion of the ammonia is volatilized and therefore lost to the atmosphere, contributing to both odor and to nitrogen enrichment of surface waters. Excess ammonia levels in water presents health problems for humans as well as animals by reducing the oxygen carrying capacity of blood. If ground water becomes contaminated, it is likely that several years will be required for the aquifer to recover.
Federal secondary effluent criteria for publicly owned treatment facilities do not include dissolved oxygen minimums. Yet, there are local discharge requirements that specify a minimum DO concentration ranging from 2 to 8 mg/L, depending on surrounding stream requirements. Generally, DO concentration levels of 2 to 4 mg/L are desirable for secondary effluents, while DO concentrations of 6 to 8 mg/L might be needed for more advanced waste systems. In order to meet these DO requirements and to aid in waste remediation, mechanical aeration equipment is used, primarily in municipal waste water facilities.
Mechanical aeration equipment is expensive to purchase, install, maintain and operate. The energy costs alone make most aeration equipment infeasible for use in agricultural operations. Obviously, there is an urgent need for an economically affordable aerobic treatment method for wastewater treatment and storage facilities.
The purpose of a mechanical aeration system is to produce the oxygen that may be used either to satisfy the BOD in biological treatment processes or to act as an agent in the oxidation of undesirable contaminants. However, mechanical aeration systems are limited in their ability to increase dissolved oxygen above certain levels.
Aerobic treatment is common in the municipal wastewater field, but, due to the high costs involved in maintaining an adequate oxygen supply, most livestock producers have selected and utilized anaerobic treatment options. Today, aerobic treatment, particularly for livestock operations, is viewed primarily as a potential supplement to anaerobic digestion for reducing odor and ammonia volatilization.
Aerobic treatment of waste can be achieved through use of a microbial agent (i.e., a microbe) whereby microbes use dissolved and suspended organic matter as a source of food. These microbes produce oxygen as a byproduct of photosynthesis, along with other byproducts which may or may not be desirable in achieving waste remediation. As such, remediation of waste water using algal and/or bacterial cultures has been known in the art for many years. Nitrogen and carbon content can be reduced by cultivation of algae and bacteria in waste waters (Baumgarten et al., 1999, Appl. Microbiol. Biotechnol. 52:281-284) and growth of algae such as Chlorella species or Scenedesmus species in waste water reduces both chemical oxygen demand (COD) and biological oxygen demand (BOD) values below the discharge limits (Hammouda et al., 1995, Ecotoxicol. Environ Saf. 31:205-210). Microalgae are also known to remove various metals from waste waters (e.g., Chan et al., 1991, Biomed. Environ. Sci. 4:250-261).
There are a number of disadvantages in current aerobic treatment methods. One current disadvantage is that many of the microbes utilized are particularly sensitive to temperature and light conditions, and such microbes only flourish in optimum light and temperature conditions. Particularly in less temperate zones where there are greater variations in daily temperature highs and lows, most microbes do not flourish, particularly in the colder winter months. Accordingly, the rate at which waste is remediated greatly drops off during the winter months. Another factor which presently limits most aerobic treatment processes is that there must be certain existing levels of dissolved oxygen and water to be available in order for the micro-organisms to be metabolically active. Particularly in agricultural operations, the waste ponds often have a thick hard and dry upper crust which carries little or no oxygen and water. Subsequently, aerobic treatment for these types of waste situations is very inefficient. Another factor which limits the effectiveness of current aerobic processes is that many microbe species are unable to effectively adapt to new environments, and the wastes which the microbes encounter may not be optimum for sufficient growth of the microbes.
A number of prior art references disclose various systems and methods for remediation of human and animal waste.
U.S. Pat. No. 3,955,318 describes a process of purifying aqueous organic waste material by mixing algae with the waste under conditions whereby the mixture is aerated using a mixture of oxygen and carbon dioxide, combined with exposure to alternating, brief periods of light and darkness. In this system, the algae are supplied to the waste water from an outside source and can include any unicellular algae such as algae from Chlorophyta, Euglenophyta, Chrystophyta, Pyrrophyta, Cyanophyta and Rhodophyta. 
U.S. Pat. No. 4,005,546 describes a method of waste treatment wherein a body of aqueous waste containing algae is transferred through multiple ponds, with each pond being exposed to different conditions. In a preferred embodiment, the first pond containing waste and algae is open to light and air. The contents of the first pond are then transferred to a second pond that is also open to light and air, where additional algae nutrients are added and the pond is continuously agitated. Finally, the contents of the second pond are transferred to a pond that is shielded from light and dark. The algae in this system naturally occur in the waste water, although algae can be reintroduced from the third, dark pond back into the first pond.
U.S. Pat. No. 4,209,388 describes a method of waste treatment which includes a first process of introducing waste into an algae containing pond which is either aerated, facultative, or a combined aerobic and anaerobic pond, followed by transfer of the waste water to a second pond where the algae are deprived of nutrients and sunlight, causing algal death and settling. The waste water is then transferred to a third pond to separate the water from the dead algae. The source and types of algae used in this system are not disclosed.
U.S. Pat. No. 4,267,038 describes a purification system for waste water in which includes steps of removal of solids from the waste water as sludge, digestion of the sludge and recombining with the waste water, a step of anaerobic, bacterial oxidation of waste water organics, followed by nutrient stabilization, nitrification, denitrification and reaeration, and then transfer of the water from the anaerobic tanks to one or more tanks containing algae and aerobic bacteria. The treated water can be channeled through a variety of tank combinations, including recycling back through anaerobic or aerobic tanks, cycling through series of aerobic tanks, and dewatering of algae for collection of the algae as a useable end product.
U.S. Pat. No. 4,966,713 describes a process for treating waste water from a food processing plant using a flocculant comprising a crude algal composition or processed algae and an acidic pH. The process produces a floc which is then separated from the water. The algae source can include Rhodophyceae, Cyanophyceae, Cholorophyceae and Phaeophyceae.
U.S. Pat. No. 6,350,350 describes a process for removing pollutants from waste water by running the waste water over a bed of algae in an attached periphyton bed. The algae are then harvested for use in a mix with a shredded paper product to produce a pulp.
In addition to these processes, various algal species have been described as being useful for bioremediation methods, being capable of utilizing waste products, or as naturally occurring within waste waters. Such algae include Chloella species and Scenedesmus species (see, e.g., Matusiak et al., 1977, Acta Microbiol. 26:79-93; Chrost et al., 1975, Acta Microbiol. Pol B 7:231-236; Matusiak, 1976, Acta Microbiol Pol 25:233-242; Chan et al., 1991, supra; Baumgarten et al., 1999, supra; Hammouda et al., 1995, supra). U.S. Pat. No. 3,882,635 describes Prototheca sphaerica FERM P-1943 as being capable of growing on a wide variety of waste waters of the food industry. This species is alleged to be superior to Chloella species with regard to the carbon sources on which these algae can grow.
U.S. Pat. No. 5,447,850 discloses a method of producing methane from organic waste. The method includes the use of aerobic microorganisms which are inoculated in the waste. The waste is then fermented with the aerobic microorganisms. The waste is also inoculated with anaerobic microorganisms. The waste is placed in an oxygen free environment, and methane is then evolved from the waste.
U.S. Pat. No. 5,755,852 discloses a nutrient rich humus material produced by a process wherein solids in an aqueous slurry of animal excrement are settled or precipitated in a solids ecoreactor, the slurry being treatable before and/or after settlement in the ecoreactor by passing to a bioreactor wherein phosphorus may be precipitated with metallic salts. Aerobic and non-aerobic treatment is used for the slurry to form an active biomass that bioconverts remaining phosphorus, nitrogen and organics. The slurry is recycled to the solids ecoreactor and/or is discharged. At least a portion of the slurry is bioconverted and recovered as a humus material.
U.S. Pat. No. 5,277,814 discloses a process for treating organic wastes. The process may be conducted in a closed reactor with controls to prevent adverse environmental impacts. The process includes mixing wastes with inert bulking agents. An oxygen containing gas is passed through the reaction mixture to assist in removal of excess water from the waste to form a wetted high solids content reaction mixture containing the waste solids mixed with the bulking agent. Aerobic reaction conditions are employed to convert the wastes to a treated waste. The aerobic reaction contemplated within this process utilizes various bacterium.
U.S. Pat. No. 5,472,472 is a related patent to the '852 patent discussed above and discloses the same invention.
U.S. Pat. No. 6,329,196 discloses a biological process enhanced by a method and apparatus used to contact a biomass with a gas and with a nutrient liquid. A compressible porous matrix system containing the biomass is mounted in a reaction vessel containing a body of the nutrient liquid and a body of the gas above the body of the liquid. The liquid has an upper surface exposed to the body of gas defining a liquid gas interface. The compressible porous matrix system is partly immersed in the liquid and extends partly above the upper surface of the liquid. The system is rotated about a horizontal axis such that there is periodic compression and expansion of regions of the porous matrix system without significant loss to the biomass.
U.S. Pat. No. 6,325,934 discloses an enzyme and bacterial combination in a slowly dissolvable matrix for septic tanks, grease traps and waste treatments. Sewage waste bacteria and enzymes are incorporated into a slow release material and delivered to the site of the waste to digest the solid waste. The slow release material is heavy so that the enzymes and bacteria will be delivered to the sludge in the bottom of the sewage digester chamber and are fat soluble so that the enzymes and bacteria will be delivered to the grease to be digested. The delivery system prevents enzymes and bacteria from being diluted in grey water which would otherwise render them less effective and would cause them to be discharged from the sewage system.
U.S. Pat. No. 6,281,001 discloses a process for composting of organic materials and for bioremediation of soils. The composting is conducted in a sealed container. The composition of the organic material is adjusted to a compostable mixture. The adjustment is done by adjusting the organic material and by mixing the organic material with a bulking agent and an inoculant. The method includes monitoring and adjusting the conditions of the composting mixture to maintain conditions within preselected limits.
U.S. Pat. No. 6,277,279 discloses a method for treating waste water by promoting growth of particular microbes capable of degrading undesirable organic material in the waste water. The method includes applying a composition that comprises fatty acids which are shown to provide greater microbial degradation. The fatty acids are preferably a combination of one or more saturated and unsaturated fatty acids. Because the unsaturated fatty acids can be in the liquid phase at room temperature, it is preferred to provide the combination of saturated and unsaturated fatty acids together to form a solid particulate at room temperature and to remain at a solid even at elevated outdoor temperatures.
U.S. Pat. No. 5,904,851 discloses a process for oxygenating a liquid. This particular invention contemplates the use of an aerobic process by carrying out a chemical or microbiological reaction in the oxygen enriched water. The invention further contemplates a therapeutic process of carrying out a treatment of the liquid with an agent containing the oxygen enriched liquid as a vehicle.
U.S. Pat. No. 5,622,864 discloses an apparatus for remediating contaminated soil containing organic compounds. More particularly, this invention is directed towards remediation of soil contaminated with hydrocarbons. The contaminated soil is placed within a container and covered by a pool of recirculating water carrying selected biological elements and chemicals to affect the remediation process.
U.S. Pat. No. 6,146,507 discloses a manure slurry pre-treatment apparatus and method for pre-treating manure. The primary purpose of the method is to alter the gas production which occurs during subsequent treatment within a manure pond. The method primarily contemplates the use of a pre-treatment zone in which the manure slurry is subjected to an alternating electrical current.
U.S. Pat. No. 5,716,523 discloses methods and compositions for treating onsite animal waste pits in order to soften the fluidized hardened solid wastes therein. The method utilizes a particular type of bacteria for the treatment.
U.S. Pat. No. 5,627,069 is a related patent to the above '523 patent and also discloses the same invention in which particular strains of bacteria are used for remediation of the waste pits.
U.S. Pat. No. 4,316,961 discloses a process for production of methane gas by anaerobic digestion of plant material and organic waste.
U.S. Pat. No. 4,432,869 discloses a method of treating animal waste which includes use of an algae/bacteria mixture culture in a separate stage. The pH-value of the algae/bacteria mixture culture is controlled in such a way that a multiplication of rotifers in this stage is inhibited or precluded. The algae/bacteria mixture culture preferably occurs in shallow open air ponds for a period of time. The hold time of the algae/bacteria suspension which is in the rotifer container is adjusted to a pH of 6-8 and can range from two to four days. The single FIGURE in this patent illustrates the basic method. The specific algae contemplated for use in this invention includes various species of chlorella or scenedesmus. 
U.S. Pat. No. 6,214,617 discloses a centrifugal fermentation process in which living cells or subcellular biocatalysts are immobilized by opposition of forces. The immobilized cells or biocatalysts may be attached to support complexes that add to the resultant vector forces. The invention can also be viewed as a method of removing contaminants from liquid comprising a biocatalyst in at least one chamber in a centrifugal force field wherein a continuous flow of liquid acts to create a force which opposes the centrifugal force field and wherein a gravitational force contributes to the resultant vector summation of all forces acting on the biocatalyst. The gravitational force, the centrifugal force and opposing liquid force substantially immobilize the biocatalyst. One of the biocatalyst includes algae cells.
U.S. Pat. No. 5,744,041 discloses a method for the step-wise reduction of biological oxygen demand of a waste material having a high concentration of organic waste. The method includes the steps of providing waste material having a biological oxygen demand and allowing the waste material to separate into a liquid fraction including water and organic waste, and allowing at least a portion of the organic waste to be anaerobically digested by microorganisms occurring in the waste. A portion of the liquid fraction having the reduced biological oxygen demand in relation to the oxygen demand of the waste material is removed and mixed with aerobic microorganisms and an aerating gas and allowing at least a portion of the organic waste to be aerobically digested by the aerobic microorganisms to form a liquor including water and suspended solids. Then, a portion of the suspended solids in the liquor is allowed to settle, forming a clarified liquor having a reduced biological oxygen demand relative to the oxygen demand of the liquor. The clarified liquor is subjected to microzone organisms from the clarified liquor to form a permeate having a reduced biological oxygen demand relative to the clarified liquid. Finally, at least a portion of the permeate is discharged or reused. In one embodiment of the process, the aerobic microorganisms comprise green algae of the genus Chlorella. 
Although these references may be adequate for their intended purposes, there still exists a need for a system and method for remediation of wastes that incorporates the use of a highly efficient microbe capable of producing large amounts of oxygen, is adaptable to various environmental conditions, and can be delivered to the waste site at a minimum cost. There is also a need for an aerobic system and method of remediation incorporating a microbe which reproduces at a high rate, thus increasing the efficiency of aerobic treatment.